carrier, in addition to the application of fuel cells operating on hydrogen-rich fuel. Water electrolysis driven by renewable energy is a promising technology [1][2][3] for hydrogen production with zero emission. Water electrolysis can be classified into the following types: alkaline, [4] proton exchange membrane (PEM), [5,6] and anion exchange membrane (AEM). [7,8] Compared to the other types, PEM-type water electrolysis is considered to be more ecofriendly and efficient because it generates no waste, produces highly pure H 2 gas (>99.9999 vol%), [9] and displays a high discharge H 2 pressure (3.0-7.6 MPa) [10] and a high current density (1.0-4.0 A cm −2 ) at low overpotentials (1.5-1.9 V). [3,6,10,11] In contrast, alkaline-and AEM-type water electrolysis produces H 2 with >99.5 vol% and >99.99 vol% purities, respectively. However, efficient electrocatalytic reactions in these systems require considerable amounts of noble metals, for example, 300 kg of Pt in the cathode and 700 kg of Ir in the anode per 1.0 GW of power input of the PEM-type electrolyzer. [11] The serious scarcity of noble metals, especially that of Ir (global production: ≈7 ton year −1 ), [11] To realize a sustainable hydrogen economy, corrosion-resistant non-noblemetal catalysts are needed to replace noble-metal-based catalysts. The combination of passivation elements and catalytically active elements is crucial for simultaneously achieving high corrosion resistance and high catalytic activity. Herein, the self-selection/reconstruction characteristics of multielement (nonary) alloys that can automatically redistribute suitable elements and rearrange surface structures under the target reaction conditions during the oxygen evolution reaction are investigated. The following synergetic effect (i.e., cocktail effect), among the elements Ti, Zr, Nb, and Mo, significantly contributes to passivation, whereas Cr, Co, Ni, Mn, and Fe enhance the catalytic activity. According to the practical water electrolysis experiments, the self-selected/reconstructed multi-element alloy demonstrates high performance under a similar condition with proton exchange membrane (PEM)-type water electrolysis without obvious degradation during stability tests. This verifies the resistance of the alloy to corrosion when used as an electrode under a practical PEM electrolysis condition.

We investigated the treatment of Fe‐Cr‐Al alloy for application in solid oxide fuel cells (SOFCs). The electrical resistance of the Al2O3‐based surface oxide layer on the alloy decreased and was stable when La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), La0.8Sr0.2MnO3 (LSM), LaNi0.6Fe0.4O3 (LNF), or Pr0.8Sr0.2MnO3 (PrSM) were first coated on the alloy and heat treated at 700 °C in air. The activation energy, calculated from the resistance, also suggested that the surface oxide became more conductive with treatment. The surface oxide layer after treatment had a microstructure of columns growing outward in the same direction, containing small amounts of elements such as Sr, Ni, Fe, La, Mn, and Pr. The microstructure consists of polycrystalline γ‐Al2O3 and small amounts of Al compounds with these elements. In the case of the LNF coating, the formation of NiAl2O4 was observed. The enhanced electrical conductivity may have resulted from the arrangement of the columnar structure, along with the electronic conduction path generated by the reaction of γ‐Al2O3 with these elements.

Introduction Recently, to decrease carbon dioxide emissions, utilization of renewable energy has been expected. Therefore, the large-scale storage and transportation of hydrogen as secondary energy is needed for effective utilization of fluctuated and unevenly distributed renewable energy. Toluene (TL) / methylcyclohexane (MCH) organic hydride system is one of the best candidates of hydrogen energy carrier because TL and MCH are liquid at ambient temperature and pressure, and it would be able to use oil infrastructure. To improve the energy conversion efficiency for TL hydrogenation using renewable electricity, we have studied direct electro-hydrogenation of TL with water decomposition using proton exchange membrane (PEM). The rate-determining step at the cathode for the hydrogenation of TL is the mass transfer of TL to the cathode catalyst layer [1]. One of the major factors that inhibit the supply of TL to the reaction field is transport water from the anode through the membrane. The accumulation of the water in the catalyst layer inhibits the supply of TL and reduces the current efficiency, but its behavior has not been clarified. In this study, the influence of current density, sulfuric acid concentration supplied to the anode and cell temperature on the amount of the transport water were evaluated in order to control the water in direct TL electro-hydrogenation electrolyzer. Experimental A DSE® (De Nora Permelec, Ltd.) for the oxygen evolution and Nafion 117® (Du Pont) were used as the anode and PEM, respectively. Carbon paper (10BC, SGL carbon ltd.) loaded with 0.5 mg cm-2 of PtRu/C (TEC61E54, Tanaka Kikinzoku Kogyo) was also used as the cathode. The cathode was hot-pressed on the PEM at 120 oC and 15 MPa for 3 min to fabricate a membrane cathode assembly. The anode and cathode compartments were circulated 0-1.5 M (= mol dm-3) H2SO4 and 10% TL/MCH, respectively. Operation temperature of the electrolyzer conducted at 50-80 oC. As the electrochemical measurement, chronopotentiometry at 0.1-0.4 A cm-2 was conducted for 20 min, and the amount of water was evaluated by measuring the weight of it in the reservoir after electrolysis. The concentration of sulfuric acid of the water was determined by measuring the pH. Results and discussion The water permeates the PEM by electro-osmosis and diffusion, and the water flux is given by eq. 1 in the images [2]. The linear region of Fig. 1 would mean water flux had linear relation to current density with constant apparent electro-osmotic coefficient with constant back diffusion flux from eq. 1. The constant back diffusion would mean that the aqueous phase is formed in the cathode catalyst layer, and its activity would be constant.Figure 1 shows dependence of cell voltage and water flux at 60 oC with various sulfuric acid concentrations on current density. There was no significant difference in cell voltages except for 0 M. Relationships between the water flux and the current density were linear except 0.1 A cm-2 at 1.5 M. The water flux decreased as the sulfuric acid conc...

New energy sources with lower environmental impact are the focus of increasing attention to enable the sustainable growth of human societies. There is an urgent need for technologies that enable conversion of renewable energy (RE) to a transportable energy carrier and recovery of that energy for later use. We have focused on organic hydrides, specifically the toluene (TOL) / methylcyclohexane (MCH) system, and have been working on a one-step process for producing MCH from TOL via electrochemical hydrogenation. We named this new method “Direct MCHTM”. The equipment needed for Direct MCH is basically the same in structure as that already used for water electrolysis. An electrolyzer with a membrane-electrode-assembly (MEA), similar to those used for polymer electrolyte water electrolysis (PEWE), can be used. The cathode consists of a carbon-supported Pt-Ru alloy catalyst with a high specific surface area and a proton-conductive ionomer. The cathode shows good electron conductivity and high diffusivity of protons and TOL, and provides a three-dimensional network of active sites. On the cathode catalyst, TOL from the diffusion layer is converted directly to MCH via electrochemical hydrogenation by protons coming from the anode through the electrolyte membrane. (Fig. 1) For process commercialization, it will be necessary to get the electrolysis voltage closer to the theoretical voltage and achieve current densities as high as those seen in alkaline water electrolysis. We also looked at how the toluene concentration affects Direct MCHTM. It has been shown that as electrolysis proceeds and the TOL concentration drops, the current density falls because it is a diffusion-limited reaction. But from the standpoint of transport efficiency, the MCH conversion rate needs to be 95% or higher, and the average current density during electrolysis to reach this rate should be comparable to that of water electrolysis, which is 0.4 A/cm2. By studying the catalyst compositions, we have made it so the percolating water through with the protons from the anode drains more easily from the cathode catalyst layer. Moreover, we obtained a cathode catalyst with high TOL diffusivity. (Fig. 2) Finally, we conducted a demonstration of the Direct MCHTM process in Queensland, Australia that was powered only by renewable energy, using electricity generated by photovoltaic cells. Over four liters of MCH obtained via Direct MCHTM was brought to Japan, showing that it is possible to transport CO2-free energy from Australia to Japan. Then, so-called "green hydrogen" was generated via dehydrogenation of the MCH and used to run a miniature car equipped with a fuel cell. Figure 1

not Available.